A fourth generation (4G) wireless network is an all Internet protocol (IP) wireless network in which different advanced multimedia application services (e.g., voice over IP (VoIP) content, video content, etc.) are delivered over IP. 4G wireless networks include a radio access network, such as, for example, a long term evolution (LTE) network or an enhanced high rate packet data (eHRPD) network. 4G wireless networks also include an IP multimedia subsystem (IMS) network and a wireless core network, referred to as an evolved packet core (EPC) network. The LTE network is often called an evolved universal terrestrial radio access network (E-UTRAN). The EPC network is an all-IP packet-switched core network that supports high-speed wireless and wireline broadband access technologies. An evolved packet system (EPS) is defined to include the LTE (or eHRPD) network and the EPC network.
Two components of the EPS are a home subscriber server (HSS) and a mobility management entity (MME). The HSS is provided in the IMS network and includes a database where user equipment (UE) subscriber profile information is stored. The MME is provided in the EPC network and is responsible for handling control plane signaling with UEs as the UEs are provided access to different packet data networks (PDNs).